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                  <h1 class="post-title">swift3-20 构造过程</h1>

                  <p class="post-byline">
                    by  · 2017年04月13日 · 669 Words ·
                    ~2min reading time |
                    <a href="https://github.com/brasbug/brasbug-hugo-blog/tree/master/content/post/2017/2017-04-13-swift20.md"
                       target="_blank">Improve on <i class="fa fa-github"></i></a>
                  </p>

                  <div class="clear"></div>

                  <div class="entry">
                    <div class="entry-inner">
                      
                      <p>构造过程是为了使用某个类、结构体或者枚举类型实例而进行的准备过程。这个过程包含了为实例的每一个属性设置初始值 的初始化任务<br />
 swift的构造函数使用的是init()方法。 这个方法没有返回值。主要任务是保证新实例在第一次使用之前完成正确的初始化。</p>

<p><strong>构造器</strong> 在创建某特定类型的新实例时调用，它的关键字是init</p>

<pre><code>init(){
    //执行属性初值设置
}
</code></pre>

<p><strong>两段式构造</strong></p>

<pre><code>class baseClass{
    var name:String
    var age:Int
    var level:String?
    init() {
        self.name = &quot;&quot;
        self.age = 0
    }
    init(name:String,age:Int) {
        self.age = age
        self.name = name
    }
    func testFunc() {
        print(&quot;baseClass&quot;)
    }
}

class sonClass1:baseClass{
    var str1:String

    init(name:String, age:Int, str1:String){
        //构造初值  第一段
        self.str1 = str1
        super.init(name: name, age: age)
        //进一步完善  第二段
        self.agefomat(age: age)

    }
    final func agefomat(age:Int){
        if age &lt;= 0 {
            self.age = 1
        }
    }
    //重载
    override func testFunc() {
        print(&quot;sonClass1&quot;)
    }
}
let son = sonClass1.init(name: &quot;a&quot;, age: 2, str1: &quot;str&quot;)
</code></pre>

<p><strong>默认属性值</strong></p>

<pre><code>class simple{
    var name = &quot;&quot;
    var age:Int
    init(){
        age = 18
    }
}
</code></pre>

<p><strong>构造参数</strong>  定义构造器 init() 时提供构造参数</p>

<pre><code>class baseClass{
    var name:String
    var age:Int
    init() {
        self.name = &quot;&quot;
        self.age = 0
    }
    init(name:String,age:Int) {
        self.age = age
        self.name = name
    }
    func testFunc() {
        print(&quot;baseClass&quot;)
    }
}
</code></pre>

<p><strong>可选属性类型</strong></p>

<pre><code>class baseClass{
    var name:String
    var age:Int
    var level:String?
    init() {
        self.name = &quot;&quot;
        self.age = 0
    }
    init(name:String,age:Int) {
        self.age = age
        self.name = name
    }
    func testFunc() {
        print(&quot;baseClass&quot;)
    }
}
</code></pre>

<p><strong>默认构造器</strong> 所有属性都设置有默认值的实例</p>

<pre><code>class simple{
    var name = &quot;&quot;
    var age = 0
}
</code></pre>

<p><strong>required 构造函数</strong></p>

<p>必须被子类实现的构造函数</p>

<pre><code>class baseClass{
    var name:String
    var age:Int
    var level:String?
    init() {
        self.name = &quot;&quot;
        self.age = 0
    }
    //子类必须实现
    required init(name:String,age:Int) {
        self.age = age
        self.name = name
    }
    func testFunc() {
        print(&quot;baseClass&quot;)
    }
}

class sonClass1:baseClass{
    var str1:String

    init(name:String, age:Int, str1:String){
        //构造初值
        self.str1 = str1
        super.init(name: name, age: age)
        //进一步完善
        self.agefomat(age: age)

    }
    private final func agefomat(age:Int){
        if age &lt;= 0 {
            self.age = 1
        }
    }
    //子类实现父类的required
    required convenience init(name: String, age: Int) {
        self.init(name: name, age: age, str1: &quot;&quot;)
    }
    //重载
    override func testFunc() {
        print(&quot;sonClass1&quot;)
    }
}
let son = sonClass1.init(name: &quot;a&quot;, age: 2, str1: &quot;str&quot;)
son.name
son.age
son.level
</code></pre>

<p><strong>构造函数的继承</strong></p>

<pre><code>class baseClass{
    var name:String
    var age:Int
    var level:String?
    init() {
        self.name = &quot;&quot;
        self.age = 0
    }
    init(name:String,age:Int) {
        self.age = age
        self.name = name
    }
    func testFunc() {
        print(&quot;baseClass&quot;)
    }
}

class sonClass1:baseClass{
    var str1:String

    init(name:String, age:Int, str1:String){
        //构造初值
        self.str1 = str1
        super.init(name: name, age: age)
        //进一步完善
        self.agefomat(age: age)

    }
    final func agefomat(age:Int){
        if age &lt;= 0 {
            self.age = 1
        }
    }
   //构造函数的继承
    override convenience init(name: String, age: Int) {
        self.init(name: name, age: age, str1: &quot;&quot;)
    }
    //重载
    override func testFunc() {
        print(&quot;sonClass1&quot;)
    }
}
let son = sonClass1.init(name: &quot;a&quot;, age: 2, str1: &quot;str&quot;)    
</code></pre>

                      
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